Re: Ada and UML

[Matteo Bordin <matteo.bordin@gmail.com>]

On Aug 31, 1:54 pm, Yannick Duchêne (Hibou57)
<yannick_duch...@yahoo.fr> wrote:
> Le Tue, 31 Aug 2010 13:05:43 +0200, Yannick Duchêne (Hibou57)  
> <yannick_duch...@yahoo.fr> a écrit:> Also, the Extend relationship, could be used to express the Ada's child  
> > package relationship. But I am not sure this is valid UML to use the  
> > extend relation between two UML packages.
>
> > And what about the Composition relationship to express Ada's nested  
> > package relationship ?
>
> To be more exact, UML Name Space should be used instead of UML Package, as  
> Ada's package are both package and name-space at a time. Just have to hope  
> that Name Space is interpreted as a special case of Package for everyones,  
> otherwise Welcome Troubles.

Hello Yannick,

UML semantics can be found in the UML metamodel superstructure at
http://www.omg.org/spec/UML/2.3/Superstructure/PDF/. As you said, UML
has no formally specified semantics - but this is also true for most
languages we use everyday (including Ada): I think it is really unfair
to keep bashing UML for not having a "formal semantics" while
basically all languages we use suffers of the same problem. The only
exceptions I am aware of are SPARK and some languages of the
synchronous family (Lustre, Esterel, ...).

Mapping Ada on UML means treating UML as graphical coding: in my
personal opinion this defeats the main purpose of UML - i.e. being a
platform-independent language. Ada profiles for UML surely exists, but
they make UML models implicitly not implementable on any other
programming language. I personally find language-specific UML profiles
a total non-sense. Having said that, it is unfortunate that an
incestuous relationship between UML and Java/C++ exists.

Anyway, one reasonable approach to represent Ada packages in
"standard" UML is to use a non extendible (isLeaf=true) UML singleton
class. Package-level variables, constants and non-primitive operations
can be mapped as static features (isStatic=True) of the singleton
class. Types declared within the Ada package can be represented as
nested non-singleton classes contained in the singleton class above (a
UML nested classifier is equivalent to Java/C++ nested classes). Ada
child packages can be mapped as nested, non-extensible singletons. As
you can see, this representation does not sound very natural from a
UML point-of-view, but covers the Ada semantics.

The extend relationships relates to UML types only: in UML, a Package
is not a type, so it cannot be extended in the UML sense. You also
cannot directly use UML NameSpace because it is an abstract semantic
element (an abstract metaclass).

Cheers,

Matteo